Over the past decade, there has been an explosion of data regarding N-acetylcysteine (NAC) biological activities, including antioxidant, anti-inflammatory, and antimicrobial activities. NAC has been used as a drug since the 1960s, in hospitals as an antidote to acetaminophen (Tylenol®) overdose, and is also on the World Health Organization (WHO) Model List of Essential Medicines. Fast forward 40 years and sold as a dietary supplement.

Supplementation with NAC has been shown to increase levels of glutathione (GSH), the body’s major antioxidant, and NAC has been found to have better bioavailability than glutathione. The depletion of both GSH and NAC leads to increased oxidative stress (an imbalance between reactive oxygen species production, also known as free radicals and antioxidant defense). This imbalance is characteristic in many conditions, including heart disease, insulin resistance, diabetes, diabetic neuropathy, neurodegenerative disease, hypertension, asthma, influenza, obesity, ischemic heart disease, and more.

More recently, the therapeutic potential of NAC is beginning to turn psychiatry on its head. Studies have shown increased benefits for psychiatric disorders, including substance abuse, depression, anxiety, schizophrenia, Alzheimer’s, autism, and bipolar disorders.

According to the American Family Physician: N-Acetylcysteine: Multiple Clinical Applications, other applications for NAC supplementation supported by scientific evidence and used by some doctors, include the prevention of chronic obstructive pulmonary disease (COPD) exacerbation, attenuation of influenza-virus symptoms, treatment of pulmonary fibrosis, and treatment of infertility in patients with polycystic ovary syndrome (PCOS).

For this article, I am focusing on two essential benefits of NAC: respiratory and immune health.

Oxidative stress is linked to the myriad of pathologies mentioned above. However, oxidative stress also plays a vital role in the first-line immune response to foreign pathogens. It activates the release of inflammatory mediators (cytokines) to amplify the body’s response by activating other immune system cells. This aspect of the immune response is also known as the inflammatory response. Cysteine supply is significant for immune health because small variations strongly influence lymphocyte and other immune cell functions in cysteine levels.

Clinical evidence for the use of NAC in acute viral respiratory tract infections is limited and, to date, relates only to small clinical trials. However, preliminary data suggest that NAC and its antioxidant properties may have a purpose for the therapy and prevention of acute viral and bacterial respiratory infections. The efficacy of NAC is likely to be viral strain dependent.

There is currently NO known proven treatment for COVID-19. However, there are several clinical trials in process, primarily on various medications and also some supplements, including the clinical trial “A study of N-acetylcysteine in patients with COVID-19 infection” listed on clinicaltrials.gov. This study will be completed in May 2021. There are additional clinical trials on NAC for other conditions, including the respiratory system’s treatment of diseases.

Patients taking NAC experienced a decrease in the deterioration of lung function, and this effect was most pronounced in patients over 50.

Studies show NAC has a positive effect on the clinical course of COPD. An open-label study of 1,392 patients found that NAC reduced the thickness and stickiness of phlegm, cough severity, and improved ease of expectoration in 80, 74, and 71% of patients, respectively, after two months. The study also reported “marked improvements” in lung sounds, shortness of breath, cyanosis, and associated heart failure. In another large trial, patients taking NAC experienced a decrease in the deterioration of lung function, and this effect was most pronounced in patients over 50.

Aging is caused by a continuous oxidation process in which the immune system is involved. The leukocyte function is generally a good health and longevity predictor, and NAC has been found to have beneficial effects on lymphocyte, neutrophil functions, and inflammation levels. Research has found that taking NAC for 2–4 months leads to the prolonged strengthening of the immune defenses in post-menopausal women and decreasing the probability of immune system-related diseases such as infections and aging.

Based on extensive research, potential benefits, and few or no side effects, it is time to bring back NAC and make it a part of your daily health and wellness program.

At the current time, there is no known proven treatment for COVID-19, however research and clinical trials are ongoing.


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